Simulating CO2 behaviour under various conditions

project-news By Hugo Ryvik
Petrell has developed a simulation system which can estimate the behaviour of CO2 under changes in flow and pressure, and under various conditions and applications, particularly with regard to formation of CO2 in solid form.
CO2 behaviour simulation
 

‚ÄčThe tool can make calculations for CO2 in process plants, during pipeline transport and in reservoirs. CO2 in solid form could potentially lead to blockages and equipment damage, and could cause safety-related problems. It is therefore important to know where and under what conditions it may arise, to ensure optimal process equipment design.

"The system is a CO2 tool for general application which can be used everywhere that CO2 is an issue," says project manager Geir Berge from Petrell.

The CO2 simulation tool was developed in a project supported by CLIMIT which started in 2011. Petrell was joined by Statoil, Total and Gassco as partners in the project.

Started in the 1990s

In the mid-1990s, Petrell started developing a multi-physical simulation tool called Brilliant. Today, both flow analysis and strength calculation are integrated in the system to achieve mutual and simultaneous interaction. In other words, a true multi-physics system.

In 1997, VessFire was built on the basis of Brilliant. VessFire calculates depressurisation in process equipment with high pressure. Depressurisation is used to reduce the pressure in components to the lowest possible hazard and damage potential.

The tool features a complex design, which includes various substances, flow properties, thermodynamics and material technology properties, the latter being particularly important when a fire occurs.

Total eventually signalled interest, and inquired whether the system could process CO2 in solid form. Petrell was ready for the challenge and an industry group was established in 2010.

Thermodynamics is the key

(Geir Berge from Petrell)The CLIMIT project has developed a new thermodynamic package based on different condition equations. The thermodynamics are incorporated in Brilliant and VessFire, and are used for calculations of physical systems and models in direct interaction with each other.

The system takes simultaneously into consideration processes in thermodynamics, flow and pipeline properties.

"The key is handling thermodynamics. We found no packages that were suitable for our need to handle CO2 in solid form in the market, so we enlisted help from NTNU (Norwegian University of Science and Technology) to adapt our own software," says Berge.

Geir Berge from Petrell headed the project. Photo: Petrell.

New algorithms

The developers made new flow equations and a separate algorithm for multi-physics systems, i.e. systems that calculate flow, energy and other factors. Strength analysis was also added.

"Connecting strength analysis with flow analysis has not been done before. They impact each other," says Berge.

The simulation system follows the CO2 through the super-critical phase where it is in a state between gas and liquid, so-called two-phase where CO2 is present both in liquid and gas form, and triple point, where CO2 in solid form is also present. The final part posed the greatest challenge for the developers.

"First we couldn't go through the triple point, we were unable to solve the phases. Luckily, we made an important breakthrough at the very end of last year, and now we can run the same algorithm through the entire system, including the triple point."

Added to Brilliant

The project was originally scheduled to end in 2013, but will now extend into 2014 due to the late breakthrough.

"Now we've been able to show that it works, and we have run simulations. It will be implemented in Brilliant over the course of the year," says Berge.

Blockages during CO2 injection

Statoil's motivation for participating in the project was that they wanted to learn whether blockages could form in the reservoir if there is a failure in a well where CO2 is injected. Scenarios of uncontrolled blowouts from the Sleipner field were modelled in Petrell's system.

The analyses showed that solid CO2 can form under certain conditions, and that measures can be carried out to prevent this.

Total has fields with high CO2 content, and wanted to know whether solids could form during depressurisation. The simulation tool has provided good answers here.

Project facts

  • Name: Simulation of CO2 in Flow and Depressurization (SolidCO2Sim)
  • Project manager: Petrell
  • Period: 2011-2014
  • Partners: Statoil, Total, Gassco
  • Budget: NOK 12.6 million
  • CLIMIT support: NOK 5.1 million

More information is available from the project's fact sheet.

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